Nuclear Stress Laboratory

Nuclear Stress Laboratory

The ICA clinic in the Texas Medical Center has an in house state-of-art nuclear stress lab. Each year ICA performs more than 1000 stress tests.

What is a nuclear stress test?

A stress test performed with injection of radiotracer (Technitium 99 isotope) intravenously, which allows detection of blood supply to the heart muscle and heart function by a special camera.

What information is available from a Nuclear Stress Test?

The study helps determine bloodflow to the heart during increasinglevels of activity. This in turn helps determine if there is blockage in the coronary circulation, previous heart damage and determine the effectiveness of a cardiac treatment plan. It also helps determine your risk of having a heart attack or death in the near future.

What types of Nuclear Stress Tests are available?

Exercise Stress Test: This is the preferred method of testing on patients who are able to exercise. The patient is made to exercise on a treadmill at increasing levels of speed and inclination to achieve an adequate level of stress. Exercise time, depending on the patient, is generally between 5-12 minutes.

Pharmacological Stress Test: This type of test is usually reserved for patients who are not able to physically exercise on treadmill. There are two pharmacological methods available:

• Adenosine Stress Test: Adenosine is a medicine that dilates blood vessels, particularly of the heart, and simulates a stress test. The adenosine is infused intravenously over 4 minutes.

Potential side effects of adenosine include warmth, flushing, chest pain, headache and heart rhythm problems. Most of the side effects dissipate completely in 5-10minutes after the infusion is stopped.

Contraindication: Patients with asthma are not candidates for this test as it can trigger an asthma attack.

• DOBUTAMINE STRESS TEST: Dobutamine is a medication that increases heart rate and heart contractility simulating a stress test without exercising. It is given intravenously at increasing dose till target heart rate is achieved.

Potential side effects: palpitations, chest discomfort, heart rhythm irregularities.

Contraindication: Your physician will determine if this test is safe for you.

How do I prepare for the test?

• Do not eat or drink anything except water for four hours before the test
• Do not drink or eat caffeine products for 24 hours before the test. Caffeine will interfere with the test results.
• Do not take any over-the-counter medication that contains caffeine for 24 hours before the test. These include Excedrin, Anacin, diet pills and NoDoz. As your doctor, pharmacist or nurse if you have questions about medications.
• Ask your doctor what medications should be taken on the day of your test. Do not discontinue any medication without first talking with your doctor.
• If you use an inhaler for breathing, bring it to the test.
• If you are diabetic, ask your physician how to adjust your medications the day of your test. Do not take your diabetes medication, and skip a meal before the test. If you own a glucose monitor, bring it with you to check your blood sugar levels before and after the test. If you think your blood sugar is low, tell the lab personnel immediately.
• Wear comfortable clothes and soft-soled shoes suitable for walking. Women should wear a bra.
• Women of childbearing age will have to sign a form indicating their last menstrual period and possibility of being pregnant. If there is possibility of your being pregnant then you are not eligible for this test.

What do I expect druring the testing?

Depending on the weight of the patient a single day/two day protocol is used.

During the stress test, IV is placed for injection of radiotracer and stressor medication (if indicated). BP and EKG are continuously monitored and patient is encouraged to report any symptoms that may develop with stress such as chest-pain/discomfort, shortness of breath, fatigue etc. Patient undergoes stress testing using treadmill/pharmacological agent as described above.

For images to be acquired, the patient has to lie under the gamma camera for about 25 minutes each for rest and stress images with left arm raised over the head.

Time duration of the entire testing: 4-5 hours.

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